U.S. patent number 4,752,826 [Application Number 06/920,559] was granted by the patent office on 1988-06-21 for intra-field recursive interpolator.
This patent grant is currently assigned to The Grass Valley Group, Inc.. Invention is credited to Ronnie D. Barnett.
United States Patent |
4,752,826 |
Barnett |
June 21, 1988 |
Intra-field recursive interpolator
Abstract
An intra-field recursive interpolator reads stored output video
from one field store while writing output video into a second field
store. The read stored output video is spatially corrected by
vertical interpolation prior to being multiplied by a decay
constant and being combined with an input video which has been
multiplied by the inverse of the decay constant to produce the
output video. The resulting output video is a combination of the
current input field of video and each preceding field of the output
video.
Inventors: |
Barnett; Ronnie D. (Nevada
City, CA) |
Assignee: |
The Grass Valley Group, Inc.
(Grass Valley, CA)
|
Family
ID: |
25443955 |
Appl.
No.: |
06/920,559 |
Filed: |
October 20, 1986 |
Current U.S.
Class: |
348/441; 345/643;
348/E5.054 |
Current CPC
Class: |
H04N
5/2625 (20130101); G09G 2310/0229 (20130101) |
Current International
Class: |
H04N
5/262 (20060101); H04N 007/12 (); H04N
005/14 () |
Field of
Search: |
;358/140,136,160,166,167
;340/728 ;375/33 ;364/723,724 ;382/54 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Groody; James J.
Assistant Examiner: Peng; John K.
Attorney, Agent or Firm: Gray; Francis I.
Claims
What is claimed is:
1. An intra-field recursive interpolator having an input interlaced
video and producing an output interlaced video comprising:
a recursive loop for storing the output video for subsequent
combination with the input video; and
means for interpolating the output video stored in the recursive
loop and combining the interpolated output video with the opposite
field of the input video to produce the output video.
2. An intra-field recursive interpolator as recited in claim 1
wherein the interpolating means comprises means for continuously
averaging a current line with the next line of the stored output
video from the recursive loop prior to combining the stored output
video with the input video to produce the output video.
3. An intra-field recursive interpolator as recited in claim 2
wherein the averaging means comprises:
means for delaying each line of the stored output video; and
means for combining each line of the stored output video with the
output of the delaying means to produce a vertically interpolated
version of the stored output video which is subsequently combined
with the input video to produce the output video.
4. An intra-field recursive interpolator as recited in claim 1
wherein the recursive loop comprises:
means for storing a current field of the output video while reading
from the storing means a prior, one field old, field of the ouput
video; and
means for multiplying the prior field of the output video by a
decay constant prior to combination with the input video to produce
the output video.
5. An intra-field recursive interpolator as recited in claim 4
wherein the storing means comprises:
a first and a second field store into which alternate fields of the
output video are written such that even fields of the output video
are written into one of the field stores and odd fields of the
output video are written into the other field store; and
means for selecting the output of one of the field stores for input
to the multiplying means, the selected field store being read from
while the other field store is being written into.
6. An intra-field recursive interpolator as recited in claim 5
further comprising means for multiplying the input video with an
inverse of the decay constant prior to combination with the stored
output video to produce the output video.
7. An intra-field recursive interpolator as recited in claim 6
wherein the recursive loop further comprises means for adding the
outputs of the two multiplying means to produce the output
video.
8. An intra-field recursive interpolator as recited in claim 5
wherein the interpolating means comprises:
means for delaying each line of the stored output video from the
selecting means; and
means for combining each line of the stored output video from the
selecting means with the output of the delaying means to produce a
vertically interpolated version of the stored output video for
input to the multiplying means.
9. An improved recursive effects device of the type wherein
alternate fields of an output interlaced video are stored
alternately in a pair of field stores, the stored output video
being multiplied by a decay constant and combined with an input
interlaced video which has been multiplied by the inverse of the
decay constant to produce the output video, the improvement
comprising:
means for reading a prior, one field old, field of the output video
from one of the field stores while writing a current field of the
output video into the other field store; and
means for vertically interpolating the stored output video from the
reading means prior to multiplication by the decay constant so that
the stored output video is spatially corrected for combination with
the input video.
Description
BACKGROUND OF THE INVENTION
The present invention relates to recursive effects devices, and
more particularly to an intra-field recursive interpolator which
interpolates between a current field and an opposite interlaced
field only one field old.
In recursive video effects devices new video is mixed with old
video to implement effects such as decay, picture trails, etc. This
is accomplished by multiplying the old video, which is stored in a
field store, by a decay constant between zero and unity. The new
video is multiplied by the inverse of this decay constant and added
to the old video as modified by the decay constant. A unity value
for the decay constant yields a frozen picture, i.e., all old
video, and a zero value yields no effect, i.e., all new video. In
an interlaced television system the field of the stored video which
is multiplied by the decay constant is combined with the
corresponding field of the new video, i.e., with video which is two
fields old. What is desired is the implementation of recursive
effects which combines the stored video with video which is only
one field old, i.e., the opposite interlaced field.
SUMMARY OF THE INVENTION
Accordingly the present invention provides a recursive interpolator
having two field stores which alternately store successive fields
of video. The outputs of the field stores are input to a
multiplexer which selects between the two outputs. The output of
the multiplexer is input to a line delay circuit and to an
interpolator, with the output of the line delay circuit also being
input to the interpolator. The output of the interpolator is mixed
with a decay constant and combined with new video which has been
mixed with the inverse of the decay constant to produce the output
video. The output video is fed back to the two field stores to
complete the recursive loop.
The objects, advantages and novel features of the present invention
will be apparent from the following detailed description when read
in conjunction with the appended claims and attached drawing.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a block diagram of an intra-field recursive
interpolator according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the FIGURE an intra-field recursive interpolator
10 is shown having an input interlaced video and an output
interlaced video. The output video is input to one of two field
stores 12, 14 alternately, i.e., one field of the output video is
stored in field store one 12, the next field of the output video is
stored in field store two 14, the third field of the output video
is stored in field store one, etc. The outputs of the field stores
12, 14 are input to a multiplexer 16 which selects one field store
for reading stored video data from while the other field store is
having a field of the output video written into it. Instead of
inputting the output of the multiplexer 16 directly into a
multiplier 18, the output of the multiplexer is input to a line
delay circuit 20 and to an interpolator 22. The output of the line
delay circuit 20 is also input to the interpolator 22 which
produces an average of consecutive lines of video from the frame
store, 12 or 14. The averaged output of the interpolator 22 is
multiplied by a decay constant, k, having a value between zero and
one. The input video is multiplied by the inverse of the decay
constant, 1-k, in multiplier 24. The outputs of the multipliers 18,
24 are combined by a summing circuit 26 to produce the output video
which is fed back to the field stores 12, 14 to complete the
recursive loop.
Table I shows the output video and contents of the field stores 12,
14 without the line delay circuit 20 and interpolator 22 assuming
that for the first two fields, F0 and F1, of input video the decay
constant is zero. Table I illustrates that when data from
television field one, i.e., the even fields, is input to field
store one 12, field store two 14 is neither being written into nor
read from. Likewise when data from television field two, i.e., the
odd fields, is input to field store two 14, field store one 12 is
neither being written into nor read from. Therefore, field store
one 12 contains only even field data and field store two 14
contains only odd field data.
TABLE I ______________________________________ Input Field Store
One Field Store Two ______________________________________ F0 F0
N/A F1 F0 F1 F2 /k*F2 + k*F0 F1 F3 /k*F2 + k*F0 /k*F3 + k*F1 F4
/k*F4 + /k*k*F2 + /k*F3 + k*F1 k.sup.2 *F0 F5 /k*F4 + /k*k*F2 +
/k*F5 + /k*k*F3 + k.sup.2 *F0 k.sup.2 *F1 F6 /k*F6 + /k*k*F4 +
/k*F5 + /k*k*F3 + /k*k.sup.2 F2 + k.sup.3 F0 k2*F1 F7 /k*F6 +
/k*k*F4 + /k*F7 + /k*k*F5 + /k*k.sup.2 F2 + k.sup.3 F0 /k*k.sup.2
F3 + k.sup.3 F1 ______________________________________
where /k=1-k.
With the interpolation circuit 21 in the recursive loop the
equations for the output video and the contents of the field stores
12, 14 are shown in Table II, assuming that F0 is input as a full
field video.
TABLE II ______________________________________ Input Field Store
One Field Store Two ______________________________________ F0 F0
N/A F1 F0 /k*F1 + {I(k*F0)} F2 /k*F2 + {I(/k*k*F1 + /k*F1 +
{I(k*F0)} k.sup.2 *F0)} F3 /k*F2 + {I(/k*k*F1 + /k*F3 + {I(/k*k*F2
+ k.sup.2 *F0)} /k*k.sup.2 *F1 + k.sup.3 *F0)} F4 /k*F4 +
(I(/k*k*F3 + /k*F3 + {I(/k*k*F2 + /k*k.sup.2 *F2 + /k*k.sup.3 *F1 +
/k*k.sup.2 *F1 + k.sup.2 *F0)} k.sup.3 *F0)}
______________________________________
As shown in Table II each field store has contributions from each
preceding field, including two field old video data from the same
television field and one field old video data from the opposite
television field. The capital "I" in these equations indicates that
the video data within the brackets is the vertically interpolated
version of this video data.
The interpolation permits the opposite field video data to have the
same spatial position as the input video data. This is accomplished
by delaying the stored video data one line in the line delay
circuit 20 and averaging the delayed line of video data with the
next line of video data output from the appropriate field store 12,
14 in the interpolator 22. This averaged video data is the
spatially corrected video data which is coincident with the
incoming video data. The second line of stored video data is input
to the line delay circuit 20 as the first line is being read from
the line delay circuit so that the averaging occurs
continuously.
Thus the present invention provides an intra-field recursive
interpolator which combines opposite television fields to produce
recursive effects by writing output video data into one field store
while reading video data from a second field store, the stored
video data from the second field store being vertically
interpolated and combined with the input video data to produce the
output video data.
* * * * *